1. Field of the Invention
The present invention relates to a method and an apparatus for inspecting cleanliness of natural fiber tops, including wool and cotton for example.
2. Background Art
Normally, the inspection of the cleanliness of wool tops is executed in accordance with the inspection method prescribed in paragraph 5.6 (ruling the number of neps) and paragraph 5.7 (ruling the number of vegetal impurities) of JIS L-1083. The cleanliness is designated by means of the number of detected defects per inspection item present in a predetermined amount of inspected top sliber.
Conventionally, the cleanliness of wool top sliber is visually inspected. Authorized inspectors visually detect and classify defects from wool top slibers aligned on an inspection table. Conventionally, a specific continuous inspection method has been executed in accordance with paragraphs 5.6 and 5.7 of JIS L-1083 by thinly and uniformly spreading top slibers in a gill box by about 0.5 mm of thickness, and then, placing sampled top slibers on an inspection table. Inspectors then visually count the number of the impurities and defects by irradiating sampled top slibers with a light beam which is permeated through an inspection window. Since inspectors are obliged to visually count the number of impurities and defects based on the conventional practice, the results of visual inspection are noticeably varied between inspectors.
In order to minimize the difference of the inspected results, only strictly selected inspectors execute the inspection of the top slibers. Nevertheless, the resultant values are not yet reliable to a full extent. Actually, the visually inspected results are merely considered to be relative values of comparison.
In order to fully solve this problem, the Applicants of the invention had previously filed an application for a patent, as per the Japanese Patent Application No. 62-303563 of 1987, on a method of classifying pillwise defects and vegetal defects from an image signal generated from an image of top slibers picked up by an image sensor. This proposed inspection method introduced a system for discerning the elongation rate in the field of pillwise defects and vegetal defects. This in turn obliged the method to follow a complex computation to extract features of the defects. As a result of a slow speed available for the feature extracting process, the method could not properly be applied to the execution of continuous inspection processes.